On the mechanism of magma injection and plate divergence during the Krafla Rifting Episode in NE Iceland
On the mechanism of magma injection and plate divergence during the Krafla Rifting Episode in NE Iceland
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冰岛东北部克拉夫拉裂谷期岩浆注入与板块分歧机制研究
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
W. Jacoby
中科院分区：
文献类型：
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作者：
G. Marquart;W. Jacoby
用简单的弹性模型分析了冰岛东北部Krafla裂缝群中100公里宽的大地测量网的水平和垂直点位移观测。从1975年到1980年，在几次岩浆注入到扩大的裂缝中的事件中，观察到的位移是累积的。裂隙群伸展沉降，邻近岩石圈收缩或挤压，地表抬升。我们应用了两种模型来拟合远场变形：无限水平压力线源或管道和无限的，垂直有限的，垂直堤坝源加载的正应力在墙壁上，都嵌入在一个弹性半空间。在远场反演中，这两种模型无法区分，但地质和观测到的轴向地堑沉降明显区别于管道和堤坝。反演结果表明，加宽的岩墙贯穿整个岩石圈，而在裂隙群中，岩墙厚度仅为4-6 km。在裂谷幕期间，1980年裂隙群中的总体岩浆水平上升到接近地表，但从1975年到1980年，负荷增量似乎有所下降。
Geodetic observations of horizontal and vertical point displacements in a ∼100-km-wide network across the Krafla fissure swarm of NE Iceland are analyzed with simple elastic models. The observed displacements accumulated from 1975 to 1980 in several events of magma injection into fissures that were widened. The fissure swarm was extended, and it subsided while the adjacent lithosphere contracted or was compressed accompanied by surface uplift. We applied two models to fit the far-field deformation: an infinite horizontal pressure line source or a pipe and an infinite, vertically limited, vertical dyke source loaded by normal stress at the walls, both embedded in an elastic half-space. In the far-field inversion the two models cannot be distinguished, but geology and the observed axial graben subsidence clearly discriminate against the pipe and for the dyke. The inversion suggests that the widened dykes cut through the whole lithosphere which in the fissure swarm is only 4–6 km thick. During the rifting episode the general magma level in the fissure swarm rose to near the surface by 1980, but the loading increments appear to have decreased whith time from 1975 to 1980.